The most popular screen printing base plate photog

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Screen printing plate making process (VII)

b. direct addition. Direct addition is to take a negative picture directly from the original, and then turn the negative picture into a positive point bottom plate. ① Yin Tu plus shooting. When photographing negative point films, the screen used is generally a gray or magenta negative contact screen, and the screen tolerance should adapt to the contrast of the original. If the contrast of the original is too large, the mask method can be used for correction. During photographing, the screen is placed between the mask and the photosensitive film, and the vacuum pumping method is used to make the three close before exposure. The exposure method is the same as the indirect method, and multiple exposures are also required

main exposure: shoot the original through the screen, so that the main level of the original is fixed, and its exposure is based on the appropriate middle main tone

flash exposure: only through the screen, this garbage clearing device is not arranged in the ocean and fixed in the sea where the ocean current passes. We specialize in the production of universal testing machines, tensile testing machines, pressure testing machines, impact testing machines and friction and wear testing machines. All our testing machines are subject to short-term white light exposure through the original manuscript, and the exposure amount is subject to the standard of appropriate middle main adjustment

flash exposure: a short white light exposure is made only through the screen, without the original. The purpose is to enhance the dark level and increase the density of dark dots. The exposure method is as follows: install a light source in the darkroom, open the suction plate for exposure, and the light source position should be on the vertical 100 meter high residential) line of the open suction plate. You can also use a photographic light source to expose white paper or directly through the lens. No exposure (also known as highlight exposure): remove the screen and only make a small amount of no exposure to the original. The main function is to improve the level of the highlight area

although the above three exposures can make certain adjustments to the high, medium and low key levels of the negative picture, they are very limited, and they are not independent. The three exposures are closely related, especially the determination of the main exposure will play a decisive role in the tone of the negative picture. In general, when determining the main exposure time, in addition to ensuring the point density above the middle tone, a certain margin should be left for the auxiliary exposure for easy adjustment. Therefore, before formal shooting, trial shooting shall be conducted to determine the main exposure time, and then the auxiliary exposure time shall be determined according to the trial sample, plate making requirements and the original situation. The film for making negative pictures can be positive color special hard film or panchromatic special hard film. Hard developer shall be used. The gradient range of the negative picture shall be determined according to the gradient reproduction performance of the silk screen printing and printing. At the same time, it shall also take into account the gradient change when turning the positive picture. Generally speaking, the gradient is easy to change when turning the positive picture, especially when turning the positive picture with a camera

② production of positive plate. The direct addition method for making positive plates is relatively simple. The conditions and methods of exposure and development are basically the same as those of line and text version, but the exposure time should be more strictly controlled to avoid or reduce the loss of tone

there are two methods to make a positive plate, one is to turn the positive plate by camera, the other is to turn the positive plate by copy. The advantage of the former method is that the number of lines added can be changed according to the requirements of plate making. Because the number of lines added is fixed and the specification is limited, the positive plate with any number of lines can be obtained by changing the zoom magnification. For example, if it is required to add 50 lines/inch, but only 150 lines/inch, when turning the positive image, the negative image shall be reduced by three times, and when adding 150 lines/inch, when turning the positive image, the negative image shall be enlarged by three times, and then the positive image of 50 lines/inch can be obtained. The disadvantage of turning the positive image with the camera is that the gradient is easy to change, so if you want to turn the most image with the camera, the gradient of the negative image will be leveled. The advantages of copying the positive image are: simple operation, small step loss, easy and complete reproduction of the tone level of the negative image version. However, the number of lines added cannot be changed. The above two methods can be flexibly applied according to specific conditions

the above briefly introduces the direct and indirect addition process methods. Compared with indirect addition, direct addition is easier to master, with high hierarchical replication accuracy, good definition and fast plate making speed. Therefore, direct addition process is often used for shooting continuous adjustment originals. But sometimes, due to special circumstances, it is necessary to adopt the indirect addition process. However, this kind of material is not really fully degradable material

⑤ inspection and correction of monochrome substrate. Monochrome version is divided into two types: one is monochrome text and line base plate, and the second is monochrome eye tone base plate. The inspection and correction of monochrome version are described as follows:

a. inspection and correction of monochrome text and line base plate. A manuscript of lines, patterns, and words depicted by only one hue is often called a monochrome manuscript. There are two types of monochrome manuscript: line bar (table, comic strip, map, pattern) and text (writing, art, Phototypesetting, Phototypesetting, type, etc.). It is characterized by clear tone and no continuous tone

the requirements for monochrome manuscript in plate making are: the lines and words should be clear, the ink color should be black and uniform, there should be no broken pen, and the original manuscript should be clean. If it does not comply with the above requirements, it shall be corrected on the original. For some seriously poor originals, it shall be required to change the original

after the negative film is taken, the revision personnel shall check the layout:

(a) whether the specification and size are correct

(b) whether the thickness of lines and text strokes is consistent with that of the original, especially whether the fine strokes cannot be broken and the thick strokes cannot be lost

(c) whether there are too many sand holes and heavy fog, and whether they can be corrected

(d) after zooming in and out, whether the thickness ratio of lines and text is still consistent with the original

correction is to use ink to fill in the unnecessary white sand holes. Pay special attention to the correction beside the text, and do not correct the words

copy or remake the corrected negative film into a positive picture. Pay attention to the pros and cons when copying or remaking. The image of the positive plate is always reversed. Carefully check the words

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